1. Field of the Invention.
The present invention involves gas furnaces. More specifically, the present invention relates to condensate traps for such furnaces.
2. Description of the Related Art.
Furnaces, particularly high efficiency furnaces operating at 90% or greater efficiency, may have a secondary heat exchanger to extract additional heat from the products of combustion and improve the overall efficiency of the furnace. Secondary heat exchangers have an undesirable side effect involving condensate which results from extracting heat from the combustion products. The increased heat extraction of the secondary heat exchanger causes the discharged products of combustion to be at a relatively low temperature. Liquid residue forms as a result of the low temperatures. In addition, the combustion of conventional hydrocarbon fuels results in the formation of various undesirable acidic compounds. These acidic compounds in the products of combustion tend to dissolve in the liquid residue, or condensate, to thereby form acidic solutions of liquid condensate.
For example, natural gas typically includes some sulfur dioxide and trioxide which forms weak sulfuric acid when dissolved in water vapor condensate. Similarly, carbon dioxide may form a weak carbonic acid in condensate. The discharge of such chemical solution should be controlled, for example, by draining the acidic condensate through a neutralizer such as disclosed in U.S. Pat. No. 4,309,947 to Tomlinson, entitled "Furnace with Flue Gas Condensate Neutralizer", assigned to the assignee of the present invention, the disclosure of which is explicitly incorporated by reference. The liquid condensate itself is separated from the discharging gases by a trap assembly, such as disclosed in U.S. Pat. No. 4,543,892 to Tomlinson, assigned to the assignee of the present invention, the disclosure of which is explicitly incorporated by reference. The trap assembly prevents the products of combustion from escaping from the furnace through the condensate drain line and entering the indoor air.
One problem with separating and collecting liquid residue in a furnace is that the condensate may deposit at any one of a variety of locations downstream from the secondary heat exchanger. To collect condensate, tubing is connected to each piece of equipment in which condensate may form. For example, a tube may be connected to the bottom of the outlet manifold from the condenser, another tube may be connected from the bottom of the connector box, and another tube may be connected from the lower end of the exhaust flue. The tubes are then connected to a trap assembly to prevent the escape of products of combustion through any of the condensate drainage lines.
In order to eliminate multiple tubes which obstruct access to the furnace, a blower and collector assembly may be used as disclosed in U.S. Pat. No. 4,892,045 to Schumacher, assigned to the assignee of the present invention, the disclosure of which is explicitly incorporated by reference. The blower and collector assembly disclosed in the Schumacher patent eliminates the multiple tubes from the various points in the furnace, providing all the drainage needed through a single condensate line.
The blower and collector assembly of the abovementioned Schumacher patent greatly improves on the design of prior art condensate drainage systems. However, a trap assembly is also a desirable component of a condensate drainage system. Trap assemblies are conventionally installed on the drainage line, usually by external mounting, in order to provide a single condensate drainage line and prevent the escape of combustion gases through the drainage line. The separate provision of a trap assembly on the drainage line introduces further complications to the installation of such a furnace, and may thereby increase the difficulty in installing or servicing the furnace.
What is needed is an improved condensate collector assembly.